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HEAT CONVECTION Just when I think we've had enough of this kind of fun, we get more! This looks like more fun than the previous project anyway. 1. Wrap a few turns of wire around a candle, allowing enough wire for a handle long enough to allow the candle to be lowered into a large bottle. Light the candle and lower it into the bottle. The candle will go out quickly because when the air in the bottle is heated, it rises and blocks the mouth of the bottle, preventing fresh air from entering. Take the candle out of the bottle. Turn the bottle upside down so that the "candle air" can escape, and swing the bottle in the air a few times to fill it with fresh air. Cut out a T-shaped piece of cardboard with a stem just wide enough to fit in the neck of the bottle. Relight the candle, and lower it into the bottle. Quickly put the cardboard T in place, and observe. Now light one end of a piece of rope, blow out the flame, and, while the rope is still smoldering, hold it first on one side of the cardboard T and then on the other. (On the heated side, the smoke will rise; on the cooler side, the smoke will go into the bottle.) I don't believe this will work. Show me. From observing the drifts of smoke, you will begin to realize that nearly all upward and downward drafts of air are caused in similar ways and that such differences in temperature cause winds. 2. Put three holes in a large wooden or sturdy cardboard box and plug the holes with corks or rubber stoppers. Over the face of the box, attach a sheet of glass or trans- parent plastic wrap which can act as a door. Light one end of a piece of rope, and blow out the flame. The rope will smolder. Place a candle in the box directly under the top hole. Light the candle, remove any two of the plugs, and hold the smoking rope near the lowest opening. (The smoke will travel from the lowest opening through the box and out a higher opening.) The openings simulate some of the possible openings in a room for proper ventilation, such as open chimney, open window, a window opened at the top and bottom, or an open door. Experiment with the box to create other air movements. Also check your own room for comparisons. When heat travels in this manner, it is called heat convection. Convection ovens can be purchased for use in your kitchens. They use less electricity than a conventional electric range oven, and do not dry out the foods as much as conventional ovens.  Any problems with this page? Send URL to
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